4 sentences

1. 他从不把这件事当事。

   tā cóng bù bǎ zhè jiàn shì dàng​shì.

   He never took this matter seriously.

   Source: Dong Chinese Dictionary

2. 这点小伤不当事。

   zhèi diǎn xiǎo shāng bù dàng​shì.

   This minor injury is no big deal.

   Source: Dong Chinese Dictionary

3. 当事双方最终达成了庭外和解。

   dāng​shì shuāng​fāng zuì​zhōng dá​chéng le tíng wài hé​jiě.

   Both parties involved finally reached an out-of-court settlement.

   Source: Dong Chinese Dictionary

4. 这件公事由他当事，处理得十分稳妥。

   zhè jiàn gōng​shì yóu tā dāng​shì, chǔ​lǐ de shí​fēn wěn​tuǒ.

   He was in charge of this official matter, and it was handled very reliably.

   Source: Dong Chinese Dictionary